Hepatitis C virus (HCV) is the most common blood-borne infection in the United States, with an overall prevalence of ~2%, and an estimated 200 million chronically infected people worldwide. A substantial body of evidence, including work from our laboratory, supports the concept that early events in the coordination and nature of multi-cellular immune responses are critical in determining whether the virus is cleared or whether persistence is established. However, despite the fact that approximately 40,000 pregnancies occur each year in HCV-infected women, little is known about the immunopathogenesis or correlates of protective immunity in this setting, in part because pregnant women with chronic HCV have hitherto been excluded from studies of immunity. For the first time, we present evidence that trophoblasts, specialized cells of the placenta that play important roles in embryo implantation and interaction with decidualized maternal uterus, can take up HCV proteins as well as respond to a viral product of hepatitis C (known as a pathogen-associated molecular pattern or PAMP) by producing high levels of Type III IFNs. These intriguing results corroborate the recent studies demonstrating genetic associations with single nucleotide polymorphisms that encode interferon lambda 3 and spontaneous recovery from HCV. Furthermore, we have identified HCV-specific CD8+ T cells within the maternal-fetal interface that we hypothesize demonstrate versatile functional attributes that prevent transmission in the majority of cases. We will also study how antigen-presenting cells in the decidua cross- present HCV antigens from trophoblasts and prime CD8+ T cells within the maternal fetal interface. Thus, our proposal seeks to mechanistically understand the different cells and signals that underpin HCV transmission versus protection.